The purpose of this project is the development of a clinical, non-invasive monitor of tissue blood flow by analysis of the spectrum of Doppler scattered laser light. The NIH Laser Doppler Blood Flow Monitor has been demonstrated to be highly portable and clinically convenient with sterilizable, rugged flexible 4m fiber optic probes and portable and photodiode detection system. The linearity of the flow analysis processor has been demonstrated in a variety of tissues and clearly resolves physiologic flow changes including instantaneous pulsatile flow in the microcirculation. Muscle blood flow in over 50 patients with neuromuscular disease has been studied and data suggest that post occulusive reactive hyperemia responses may be primary of secondary indicators of disease state. Studies of scleroderma patients' skin blood flow have shown reduction in flow correlates well with disease state. Nasal Blood flow is being assesed as quantitative measure of allergic and drug responses in the nose.